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← IIT-JEE 2010 · Paper 2
ChemistryMatrix match+8Question 18 of 57

IIT-JEE 2010 · Paper 2, Chemistry question 18

Match the reactions in Column I with appropriate options in Column II.

Column I

  • A
    Benzenediazonium chloride + phenol →0 ∘CNaOH/HX2O\xrightarrow[0\,^\circ\mathrm C]{\ce{NaOH/H2O}} 4-hydroxyazobenzene (CX6HX5−N=N−CX6HX4−OH\ce{C6H5-N=N-C6H4-OH})
    Benzenediazonium chloride and phenol in NaOH/H₂O at 0 °C give 4-hydroxyazobenzene.
  • B
    (CHX3)X2C(OH)−C(OH)(CHX3)X2→HX2SOX4CHX3CO−C(CHX3)X3\ce{(CH3)2C(OH)-C(OH)(CH3)2 ->[H2SO4] CH3CO-C(CH3)3}
    Pinacol (2,3-dimethylbutane-2,3-diol) with H₂SO₄ gives pinacolone (3,3-dimethylbutan-2-one).
  • C
    Acetophenone →2. HX3OX+1. LiAlHX4\xrightarrow[\text{2. } \ce{H3O+}]{\text{1. } \ce{LiAlH4}} 1-phenylethanol (CX6HX5CH(OH)CHX3\ce{C6H5CH(OH)CH3})
    Acetophenone reduced by 1. LiAlH₄, 2. H₃O⁺ to 1-phenylethanol.
  • D
    4-Chlorocyclohexanethiol (HS−CX6HX10−Cl\ce{HS-C6H10-Cl}) →Base\xrightarrow{\text{Base}} 7-thiabicyclo[2.2.1]heptane (S bridging C1 and C4)
    4-Chlorocyclohexane-1-thiol with base cyclises to the bridged sulfide 7-thiabicyclo[2.2.1]heptane.

Column II

  • P
    Racemic mixture
  • Q
    Addition reaction
  • R
    Substitution reaction
  • S
    Coupling reaction
  • T
    Carbocation intermediate
Mark every match for each entry
PQRST
A
B
C
D
Answer and worked solution

Official answer: A → R, S; B → T; C → P, Q; D → R

  • A, diazo coupling. The diazonium ion attacks the activated para position of phenoxide, replacing H: an electrophilic substitution that is also a coupling reaction. → R, S.
  • B, pinacol rearrangement. Protonation and loss of water give a tertiary carbocation, which undergoes a 1,2-methyl shift to pinacolone. → T.
  • C, LiAlH₄ reduction. Hydride adds to the C=O of acetophenone; attack from either face of the planar carbonyl gives a racemic mixture of 1-phenylethanol. → P, Q.
  • D, intramolecular cyclisation. The base forms a thiolate that displaces chloride (intramolecular SN2\mathrm S_\mathrm N2, substitution), bridging C1 and C4. → R.

Answer: A → R, S; B → T; C → P, Q; D → R

Topics:Reaction types and mechanismsDiazonium saltsAlcoholsOxidation and reduction
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